Combination rocket and ramjet engines are well known as exemplified by U.S. Pat. No. 3,535,881 to patentee Schubert. Solid fuel ramjet engines are also known as shown by Chandler in U.S. Pat. No. 2,799,987. The prior art combination rocket and ramjet engines have had the problem of the metallic walls of the combustion chamber becoming too hot and melting during the cruise portion of the flight.